1. Field of the Invention
The present invention is directed to a communication system that includes at least two private branch exchanges respectively having an exchange controller and at least one switching node that is connected via a network termination device [sic] to at least one higher-ranking communication network and that is connected via at least one subscriber line to terminal equipment. As such a team function controller is provided in one of the private branch exchanges, for controlling specific terminal equipment according to a team function as team terminal equipment of a team. Such can be called via the switching node of this private branch exchange wherein the controller can initiate a signalling to other team terminal equipment dependent on the switching-oriented condition of individual team terminal equipment as well as influence their switching-oriented condition.
2. Description of the Prior Art
Such interconnected private branch exchanges, a team function being realized in at least one thereof, are known, for example, in the form of the private branch exchange HICOM 300 commercially distributed by Siemens AG. For example, one known team function is the xe2x80x9ccall pickupxe2x80x9d function, wherein incoming calls are displayed within a call pickup group composed of a plurality of exchange equipment and can be accepted at any terminal equipment that belongs to the call pickup group. Another known team function is the xe2x80x9ccollective linexe2x80x9d function that can be reached under a specific collective number. Each party of a collective line thereby also can be directly called via an individual telephone number. However, all parties are reached via the specific collective number. For example, the collective number is allocated to a master terminal equipment. Another known team function is the integrated reception system that is also referred to as a boss-secretary system.
In known communication systems, all members of a team are connected to a single private branch exchange and are switched to a higher-ranking communication network via the same network termination device.
An object of the present invention therefor is to offer a communication system wherein a team function also can be realized with detached team members.
According, the present invention. That at least one first team terminal equipment of the team is directly connected to a switching node of the first private branch exchange via a subscriber line and at least one second team terminal equipment, as detached member of the team, is connected to a switching node of the second private branch exchange as terminal equipment via a subscriber line unit. As such, this detached member can be reached via the switching node of the via first private branch exchange, a hot-line connection between the first and the second private branch exchange and via a switching node of the second private branch exchange.
A team function sub-controller is provided in the second private branch exchange in order to switch an outgoing call from the team terminal equipment into the higher-ranking communication network via the hot-line connection and the switching node of the first private branch exchange and, given a malfunction of the hot-line connection or of the switching node of the first private branch exchange, in order to switch an outgoing call from the second team terminal equipment via the network termination device of the second private branch exchange.
The connection of team terminal equipment as detached members via a hot-line connection makes it possible to arrange members of a team within a company network at an arbitrary spatial distance from one another. The inventive team function sub-controller in the private branch exchange to which the team terminal equipment of the detached member is directly connected assures that calls outgoing from team terminal equipment of detached members can be switched into the higher-ranking communication network even given outage of the hot-line connection to the home switching node of the team or given outage of this home switching node.
A beneficial embodiment of the inventive communication system provides that the team function sub-controller acquires the availability of the switching node of the first private branch exchange and the availability of the hot-line connection between the two private branch exchanges by checking the signalling connection required for the transmission of the subscriber-to-subscriber messages for the remote members. In this case, the availability check does not require any B-channel resources. Further, no additional signalling is required.
Additional features and advantages of the present invention are described in, and will be apparent from, the Detailed Description of the Preferred Embodiments and the Drawings.